1. Field of the Invention
This invention relates to bi-directional and multi-axial fabrics, fabric composites, ballistically resistant assemblies thereof, and the methods by which they are made.
2. Description of the Related Art
Ballistically resistant fabric-based composites have typically been formed from layers of fabrics that are plied together. The fibers in a fabric can be woven, knitted and/or non-woven. Where the individual fabric plies include non-woven and unidirectionally oriented fibers, successive plies are usually rotated relative to one another, for example at angles of 0°/90° or 0°/45°/90°/45°. The individual fabric plies are generally either uncoated or else embedded in a polymeric matrix material which fills the void spaces between the fibers. If no matrix is present, the fabric or fiber sheet is inherently flexible. A contrasting type of construction is a composite consisting of fibers and a single major matrix material. To construct rigid composites of this type, individual plies are bonded together using heat and pressure to adhere the matrix in each ply, forming a bond between them, and consolidating the whole into a unitary article.
These earlier constructions have several disadvantages. Woven or knitted fabrics generally have poorer ballistic resistance than cross-plied unidirectional fiber composites. On the other hand, woven or knitted fabrics can be produced at lower cost and greater ease of manufacture with more commonly available equipment than can cross-plied unidirectional fiber composites.
A need therefore exists for a fabric construction that retains the advantages of lower cost and greater ease of manufacture, but that has ballistic resistance superior to conventional fabrics. Ideally, the fabric construction would be highly flexible and capable of being bonded to itself or to hard facings to form rigid panels.
U.S. Pat. No. 4,737,401 discloses ballistic resistant fine weave fabric articles. U.S. Pat. Nos. 5,788,907 and 5,958,804 disclose ballistically resistant calendered fabrics. U.S. Pat. No. 4,623,574 discloses simple composites comprising high strength fibers embedded in an elastomeric matrix. U.S. Pat. No. 5,677,029 discloses a flexible penetration resistant composite comprising at least one fibrous layer comprised of a network of strong fibers, and at least one continuous polymeric layer coextensive with, and at least partially bound to a surface of one of the fibrous layers. Aramid fabrics rubber coated on one or both sides are commercially produced by Verseidag Industrietextilien Gmbh. under the product name UltraX. Rigid panels formed by bonding the rubber-coated fabrics together under heat and pressure are also available.
In another context, U.S. Pat. No. 2,893,442 discloses a bi-directional woven fabric having transverse sets of straight and parallel high strength, high modulus yarns interleaved with thin binder yarns. A bi-directional knitted fabric having transverse sets of straight and parallel high strength, high modulus yarns interleaved with thin binder yarns is disclosed in a publication by S. Raz, “Eine Auswahl optimaler Geotextilien,” Tettilinfomationen Kettenwir-Praxis, (2), 35-39 (1990). A multi-axial warp knit fabric is disclosed in “Wellington Sears Handbook of Industrial Textiles”, S. Adanur, Ed., Technomic Publishing Co., Inc., Lancaster, Pa., 246-247 (1995).
Each of the constructions cited above represented progress toward the goals to which they were directed. However, none described the specific constructions of the fabrics, fabric composites and assemblies of this invention, and none satisfied all of the needs met by this invention.